Transmitting apparatus for railway train communication systems



March 16, 1943. A. M. CRAVATH 2,313,924

TRANSMITTING APPARATUS FOR RAILWAY TRAIN COMMUNICATION SYSTEMS Filed June 5, 1942 [NVE/VTOR.

HLSAHURNEK Patented Mar. 16, 1943 UNITED ST res T [CE I TRANSMITTING APPARATUS FOR RAILWAY TRAIN COMMUNICATION SYSTEMS Application June 3, 1942, Serial No. 445,566

10 Claims.

My invention relates to transmitting apparatus for railway train communication systems,

and more particularly to transmitting apparatus for a communication system that uses the track rails as part of the transmitting circuit.

In systems of this character, the railway train is often equipped with a sending loop circuit which conductively couples the transmitting apparatus to the track rails for supplying current to the transmitting circuit. Such a sending loop circuit is formed by connecting one terminal of the transmitting apparatus to one pair of wheels of the vehicle and the other terminal to another pair of wheels of the vehicle, the rails in multiple between these two spaced pairs of wheels forming one side of the loop circuit, and a conductor extending along the body of the vehicle forming the other side of such circuit. The current set up in this loop circuit by the transmitting apparatus is ordinarily of relatively large magnitude in, order to create across the length of rails between the two spaced pairs of wheels a voltage sufiicient to cause communication current, which is usually a modulated carrier, of an eifective value to flow in the rails in multiple in one direction from the vehicle at any given instant and return to the vehicle through the ground path and the rails in multiple. The current flowing in such loop circuit, which is substantially a closed loop, creates a magnetic field that induces electromotive forces in line wires mounted on a pole line extending along the railway and may thereby cause interference in the telegraph, telephone or signaling circuit completed over such line wires.

A feature of my invention is the provision in a railway train communication system of train carried transmitting apparatus incorporating novel means to avoid interference with circuits having line wires extending along the railway.

Another feature of my invention is the provision of train carried transmitting apparatus of the type here involved incorporating novel circuit means having a magnetic moment which is substantially equal and opposite to the magnetic moment of the usual sending loop circuit.

Other features, objects and advantages of my invention will appear as the specification progresses.

The features and advantages embodying my invention I obtain by providing an additional circuit means on a vehicle of a railway train on which there is mounted transmitting apparatus using a sending circuit electrically coupled to the rails, and which additional circuit means is connected to the transmitting apparatus in parallel with the regular sending circuit and is constructed to have a magnetic moment substantially equal and opposite to that of the regular sending circuit. In other words, I provide a train carried additional circuit which is connected to the transmitting apparatus in parallel with the regular sending circuit, and which additional circuit is disposed to induce in a line wire extending along the railway an electromotive force that neutralizes the electromotive force induced in such line wire from the regular sending circuit.

I shall describe three forms of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a schematic View showing one form of train carried transmitting apparatus embodying my invention. Fig. 2 is a view, partly diagrammatic and partly sectional, showing the inductive relationship of the apparatus of Fig. l to line wires. Fig. 3 is a view, partly diagrammatic and partly in section, showing a modification of the appa-v ratus of Fig. 1 that I may use. Fig. 4 is a schematic view showing another form of train carried apparatus embodying my invention.

In each of the several views like reference characters are used to designate similar parts.

Referring to Fig. 1, the reference characters RI andRZ designate the track rails of a railway and the dotted rectangle Vl designates a vehicle of a railway train.

Transmitting apparatus shown conventionally at TA is mounted on vehicle VI. The apparatus TA may be any one of several different forms and may be, for example, that covered by Letters Patent of the United States No. 2,064,639, granted December 15, 1936 to L. D. Whitelock et al. for Communicating system. It is sufficient for the present application to point out that transmitting apparatus TA is operative to supply an oscillating current such as a carrier telephone current. In a communication system of the type here contemplated, the track rails Bi and R2 in multiple are included in the transmitting circuit, the circuit being completed through the rail-to ground impedance. The transmitting apparatus TA is coupled to the transmittin circuit by being coupled to the track rails Bi and R2, and preferably it is conductively coupled to the rails through the medium of a sending loo-p circuit which includes two spaced pairs of wheels of vehicle Vi. Looking at Fig. 1, the sending loop circuit can be traced from terminal T l of apparatus TA through a conductor 4 running lengthwise of the vehicle to the left-hand end of the vehicle, axle A2, wheels W3 and W4 in multiple to rails 33! and respectively, then through these rails in multiple to wheels W! and W2, respectively, axle Al, and a conductor 5 to the other terminal T2 of apparatus TA. Electrical contact between conductor 4% and axle A2, and between conductor and axle Al may be accomplished by any one of several different arrangements, such for example,

as that covered by Letters Patent of the United States No. 2,064,642, granted December 15, 1936 to P. N. Bossart, for Railway train communication systems. The direction of the flow of current in the sending loop circuit at a given instant is indicated by arrows placed on th different elements of the circuit. It is clear that conductor 4 forms one side of this loop circuit and the rails RI and R2 in multiple form the other side of such circuit, and that a voltage is developed along the rail length between the two pairs of wheels due to the current flowing in the sending loo-p circuit. Furthermore, such voltage developed along this length of rails will cause communication current to flow in the rails in multiple from one end of the vehicle, through th rail-to-ground impedance and back to the rails in multiple at the other end of the vehicle. I prefer to locate conductor 4 relatively low and, as shown in Fig. 2, conductor 4 is positioned beneath the body of the vehicle. It is to be understood, however, that my invention is not limited to any particular location on the vehicle for the conductor 4.

According to my invention an additional circuit is provided for vehicle VI. This additional circuit passes from terminal Tl of transmitting apparatus TA, through conductor 4, conductor 6, conductor 1 running lengthwise along the vehicle, conductor 8, impedance 9 and conductor 5 to terminal T2 of apparatus TA. Arrows have been placed on this additional circuit to show the direction of the flow of current at the instant current is flowing in the regular loop circuit in the direction indicated by the arrows placed on that circuit. Conductor I of this additional circuit is preferably positioned on the vehicle somewhat higher than conductor 4 and in Fig. 2 conductor 1 is shown as located above the vehicle body. For example, conductor '1 may be located along the roof of a caboose. The total current output of transmittin apparatus TA divides between the regular loop circuit and this additional circuit according to their relative impedances and the current flowing in each circuit creates a magnetic field transverse to the track rails. The general directions of such magnetic fields are indicated by the light curved lines of Fig. 2, and it is clear that electromotive forces would be induced by these magnetic fields in line wires LI and L2 mounted on a pole line along the railway, pole It] being one pole of such a pole line. Such induced electromotive forces in line wires Li and L2 may interfere with any circuit completed over these line wires. The magnetic fields created by the regular loop circuit and the additional circuit are opposite in direction due to the relative positions of the two circuits. The additional circuit is so located and the value of the current flowing therein with respect to the current flowing in the regular loop circuit is so proportioned by impedance 9 that the two magnetic fields create electromotive forces in line wires LI and L2 that substantially neutralize each other. If this neutralization is made substantially perfect for line wires LI and L2 at a given position with respect to the track, it will hold approximately for a line wire extending along the railway at any other position with respect to the track.

It may be desirable to form the regular loop circuit by making the side of the circuit which extends lengthwise of the vehicle consist of two or more conductors in parallel and at substantially the same height. An arrangement that has been found to create practically no interference field is shown in .Fig. 3, where the regular loop circuit includes in parallel two conductors 4a and ib extending lengthwise of the vehicle, conductor 4a being located under one edge of the vehicle body, and conductor 4b being located under the other edge of the vehicle body. The metal body of the vehicle itself serves as the return conductor corresponding to conductor 1 of Fig. 1 for the additional circuit. In this case of Fig. 3 the impedance for the additional circuit consists of the impedance of the connections to the vehicle body.

The essential thing about apparatus embodying my invention is the provision of an additional circuit having transverse symmetry and providing a magnetic moment substantially equal and opposite to that of the regular sending loop circuit. It is apparent that the circuits disclosed in Figs. 1, 2 and 3 provide such results. Another form of circuit means for accomplishing these results is shown in Fig. 4. Here primary winding it of an output transformer T3 is supplied with communication current from transmitting apparatus TA. One secondary winding l2 of transformer T3 is connected to a regular loop circuit comprising a conductor 13, rails RI and R2 and two spaced pairs of wheels of the vehicle on which the apparatus is mounted, as will be readily understood by an inspection of Fig. 4. Another secondary winding E4 of transformer T3 is connected to an additional circuit including a coil L3 mounted on the vehicle in a vertical plane. A condenser [5 is preferably connected across winding [2, and a condenser I6 is preferably connected across secondary winding 14 of transformer T3. It is apparent that by proper proportioning of the parts the magnetic moment of the circuit including coil L3 can be made substantially equal and opposite to that of the regular loop circuit, and when such an arrangement is effected interference with circuits completed over line' wires running parallel to the railway is substantially avoided.

Although I have herein shown and described but three forms of transmitting apparatus for railway train communication systems embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with transmitting apparatus mounted on a railway vehicle for supplying communication current, a sending circuit connected to said transmitting apparatus and disposed on said vehicle for electrical coupling to the track rails for transfer of communication current to the rails, and an additional circuit connected to said transmitting apparatus in parallel with said sending circuit and disposed to have a magnetic moment substantially equal and opposite to the magnetic moment of said sending circuit.

2. In combination with transmitting apparatus mounted on a railway vehicle for supplying communication current, a conductor mounted lengthwise on said vehicle and provided at each end with electrical connections to the track rails in multiple to form a sending circuit conductively coupled to the rails, said sending circuit being connected to said transmitting apparatus for transfer of said communication current to the rails, and an additional circuit connected to said transmitting apparatus to receive communication current in parallel with said sending circuit and disposed on said vehicle in a position to create a magnetic field which substantially neutralizes the magnetic field created by said sending circuit.

3. In combination with transmitting apparatus mounted on a railway vehicle for supplying communication current, a sending circuit including a conductor mounted lengthwise on said vehicle and two spaced pairs of wheels of the vehicle, said sending circuit being connected to said transmitting apparatus for transfer of communication current to the rails due to the conductive coupling of the sending circuit with the rails, another circuit mounted on said vehicle above said sending circuit and connected to said transmitting apparatus to create a magnetic field of a direction opposite to the magnetic field created by said sending circuit, and impedance means interposed in said other circuit to cause the magnetic field created by said other circuit to substantially neutralize that created by said sending circuit.

4. In transmitting apparatus for a railway train communication system, the combination comprising, a railway vehicle having mounted thereon transmitting apparatus for supplying a carrier communication current; a sending loop circuit including two spaced pairs of wheels of the vehicle, the track rails between such spaced pairs of wheels and a first conductor extending lengthwise of the vehicle and said circuit being connected to said transmitting apparatus to receive communication current, an additional circuit including said first conductor and another conductor extending lengthwise of the vehicle at a location above said first conductor and said additional circuit connected to the transmitting apparatus to receive communication current, and impedance means interposed in said additional circuit to predetermine the value of the current flowing in the additional circuit to create a magnetic field substantially equal and opposite to that created by the current flowing in the sending loop circuit.

5. In transmitting apparatus for a railway train communication system, the combination comprising, a railway vehicle having mounted thereon transmitting apparatus for supplying a carrier communication current, a sending loop circuit connected to said transmitting apparatus to receive such communication and including a first conductor extending lengthwise of the vehicle beneath the body of vehicle and other conductors connected to the wheels of each of two spaced pairs of wheels of the vehicle, an additransmitting apparatus for supplying a carrier,-

communication current, a sending loop circuit including a conductor extending lengthwise of the vehicle and two spaced pairs of wheels of the vehicle and said sending circuit being coupled to the transmitting apparatus to be supplied with the communication current, and an additional circuit including a winding disposed in a vertical plane on the vehicle above the said sending circuit and said additional circut coupled to the transmitting apparatus to receive communication current to create a magnetic field substantially equal and opposite to that created by said sending loop circuit.

7 In transmitting apparatus for a railway train communication system, the combination comprising, a railway vehicle having mounted thereon transmitting apparatus for supplying a carrier communication current; a regular sending circuit including a conductor extending lengthwise of the vehicle, connections to two spaced pairs of wheels of the vehicle and th track rails in multiple between such pairs of wheels; an additional circuit including a coil disposed to have transverse symmetry and a magnetic moment equal and opposite to that of said regular sending circuit, and means to couple said transmitting apparatus to said sending and additional circuits in parallel.

8. In combination with transmitting apparatus on a railway vehicle for supplying communication current, a sending circuit connected to said transmitting apparatus and disposed on said vehicle for electrical coupling to the track rails for transfer of communication current to the rails, and an additional circuit means connected to receive current from the transmitting apparatus and disposed on said vehicle to have a magnetic moment substantially equal and opposite to the magnetic moment of said sending circuit.

9. In combination with transmitting apparatus mounted on a railway vehicle for supplying communication current, a circuit means including a first and a second portion and. connected to said transmitting apparatus to receive current therefrom, said first portion disposed on said vehicle for conductive coupling to the track rails for transfer of communication current to the rails, and said second portion proportioned and disposed on the vehicle with respect to said first portion to create a magnetic field which substantially neutralizes the magnetic field created by said first portion.

10. In transmitting apparatus for a railway train communication system, the combination comprising a railway vehicle having mounted thereon transmitting apparatus for supplying a communication current, circuit means including a first and a second circuit path connected to said transmitting apparatus to receive such communication current, said first circuit path including a first conductor extending lengthwise of the vehicle and other conductors connected to two spaced pairs of wheels of said vehicle to cause such communication current to flow in the track rails, and said second circuit path including a second conductor extending lengthwise of the vehicle at a location above said first conductor to create a magnetic field substantially equal and opposite to that created by the current flowing in saidfirst circuit path.

AUSTIN M. CRAVATH. 

